Process for treatment of liquors using multi-compartment baths

ABSTRACT

An improvement is shown in cell process and apparatus for the electrolytic separation of components from electricallyconductive liquor containing dispersed ionizable material electrodepositable on a deposition electrode to build substantial electrical resistance thereon and dissolved ionizing agent therefor, e.g., an aqueous dispersion of electrocoating paint. A primary electrode, charged from an external source, is maintained at each electrical extremity of a body of the liquor, and at least one secondary electrode pervious to ions of the liquor is interposed between the primary electrodes. The secondary electrodes compartment the body into a plurality of zones communicating with each other through such secondary electrodes. Electrical potential between the primary electrodes is applied with the potential between adjacent electrode pairs insufficient for causing electrodeposition on any of the secondary electrodes. An anolyte-enriched liquid and a catholyte-enriched liquid concentrate at the extreme compartments. If desired, the primary electrode opposite the deposition electrode also can be made porous for percolation of electrolyte solution through such primary electrode. Additionally, the deposition electrode can be made porous, and operated for electrodeposition of said ionizable material with the passage of same through such deposition electrode.

nile tats atent 1 1 i w Gilchrist [4 1 on. in, lots lPlRUClESS FORTREATMENT 0F LlQ UCiRS USING MULTll-CUMlPAlIlTMlEN'Il BATH-11S Inventor:Allan 1F. Gilchrist, Westlake,

Ohio... V.

Assignee: SCM Corporation, Cleveland,

Ohio

Filed: May l7, 1972 Appl. No.: 253,933

lllelated US. Application Data Division of Ser. No. 99,120, Dec. 17,1970, and a continuation-in-part of Ser. Nos. 76,311, Sept. 28, 1970,abandoned, and Ser. No. 91,905, Nov. 23, 1970, abandoned, and Ser. No.94,267, Dec. 2, 1970, abandoned.

[52] US. Cl. 204N180 ll, 204/299, 204/181,

204/301 llnt. Cl Ellllt 5/00, BOlk 5/02 lField oil Search 204/180 R, 180P,

[56] References Cited UNITED STATES PATENTS 3/1908 Christy 204/2688/1959 Metcalfe et al.... 204/300 10/1965 Juda 204/299 X 6/1972 Lohr204/181 Primary Examiner-John H. Mack Assistant Examiner-A. C. PrescottAtt0rney-Merton H. Douthitt et al.

[5 7] ABSTRACT An improvement is shown in cell process and apparatus forthe electrolytic separation of components from electrically-conductiveliquor containing dispersed ionizable material electrodepositable on adeposition electrode to build substantial electrical resistance thereonand dissolved ionizing agent therefor, e.g., an aqueous dispersion ofelectrocoating paint. A primary electrode, charged from an externalsource, is maintained at each electrical extremity of a body of theliquor, and at least one secondary electrode pervious to ions of theliquor is interposed between the primary electrodes. The secondaryelectrodes compartment the body into a plurality of zones communicatingwith each other through such secondary electrodes. Electrical potentialbetween the primary electrodes is applied with the potential betweenadjacent electrode pairs insufficient for causing electrodeposition onany of the secondary electrodes. An anolyte-enriched liquid and acatholyte-enriched liquid concentrate at the extreme compartments. Ifdesired, the primary electrode opposite the deposition electrode alsocan be made porous for percolation of electrolyte solution through suchprimary electrode. Additionally, the deposition electrode can be madeporous, and operated for electrodeposition of said ionizable materialwith the passage of same through such deposition electrode.

7 Claims, 1 Drawing Figure I 54 l at 4 q 55 L )2 IPTTQCIESS IF 011TTREATMENT 01F LTQIUURS IUSIING MULTT-TJTTMIPARTMTENT MATHS This is adivision of application Ser. No. 99,120, filed Dec. 17, 1970.

This patent application is also a continuation-impart of my copending U.S. Pat. application, Ser. No. 76,311, filed Sept. 28, 1970 nowabandoned, Ser. No. 91,905, filed Nov. 23, 1970 now abandoned, and Ser.No. 94,267, filed Dec. 2, 1970 now abandoned, the teachings of which areincorporated by reference.

This invention is an improvement in cell process and apparatus for theelectrolytic separation of components from an electrically-conductiveliquor containing dispersed ionizable material electrodepositable on adeposition electrode to build substantial electrical resistance thereonand dissolved ionizing agent therefor. The process and apparatus areespecially adaptable to treating aqueous electrocoating paintdispersions and rinse waters from electrocoating operations. Treatmentof other liquors in accordance with the invention principles, e.g.,pigmented dispersions, sewage, black liquor from crude sulfate pulping,and plant and mine wastes containing electrodepositable slimes andgel-formers also are contemplated.

l-ieretofore it has been proposed to separate aqueous solutions of mixedmetalliferous electrolytes through a pair of opposed porous primaryelectrodes at voltage too low to cause the metals to electroplate onelectrodes whereby the ensuing electrically-stressed percolation wasstated to yield fairly pure materials in a cascading arrangement (U. S.Pat. No. 1,603,298). In another proposal (U. S. Pat. No. 2,905,604)black liquor from sulfate pulping of wood is electrolytically treated tocoat out lignin on the anode. The art of electrolytically producingcaustic soda and chlorine from sodium chloride is replete with the useof perforated electrodes, as generally is that of electrolytepurification, e.g., acetic acid solutions and the like.

In the art of electrocoating of paint, with the paint attracted to ananodic substrate, removal of excess of offending basic ions from thepaint bath has been proposed by means of dialysis, ion exchange andvarious species of electrodialysis such as those using rigid ordeformable or ion exchange membranes. Principal patents in this fieldinclude my U. S. Pats. No. 3,230,162 of Jan. 18, 1966, and No. 3,304,250of Feb. 14, 1967, wherein a pH of the electrocoating bath is shown to bemaintained by electrodialysis while an electrode substrate is beingcoated. Also illustrative are U. S. Pat. Nos. 3,419,488 and 3,496,083,and Japanese Pat. Publication No. 13231/1970 of May 13, 1970.

To concentrate and/or reclaim electrocoating baths or waste waterstherefrom, e.g., rinse waters, for reuse or disposal, it has beenproposed to use ultrafiltration and reverse osmosis techniques. Theseboth can be effective, but are costly because the equipment used isessentially of low capacity per unit of invested capital. Recently(Sept. 21, 1970, CELEN, page 39), a closedloop system of applyingultrafiltration to electrocoating paint baths was announced. in theelectrodeposition of rubber a gas-permeable anode was proposed wherebythe gases are withdrawn from the anode rearwardly (U. S. Pat. No.1,583,704).

The instant invention provides an attractive way to treat the subjectliquors electrolytically. It provides a way for concentrating andrecovering electrocoating binder resins and paint components, dewateringelectrocoating baths, and generally providing for the treatment ofvarious electrically-conductive liquors with a plurality of quite coarseporous electrodes having high flow capacity. The effluents from the unitcan be further treated in similar apparatus or recycled to the sameapparatus, or conducted into other conventional processing devices forfurther treatment, e.g., ion exchange, distillation, such as vacuumdistillation, filtration, ultrafiltration, reverse osmosis, dialysis,electrodialysis, neutralization, and the like.

In one aspect my invention is a process for treating the subjectelectrically-conductive liquors to concentrate anolyte-enriched andcatholyte-enriched liquids from said liquor. The process comprises:forming a body of said liquor with primary opposed electrodes at itselectrical extremities, said primary electrodes obtaining their chargefrom a source external to said body; interposing between said primaryelectrodes at least one secondary electrode deriving its charge from theelectrical conductivity of said body, at least the secondary electrodesbeing pervious to the ions in said body and compartmenting said bodyinto a plurality of zones communicating with each other through saidsecondary electrodes; and applying an electrical potential between saidprimary electrodes with the resulting potential between adjacentelectrode pairs being insufficient for causing electrodeposition of saidionizable material on any of said secondary electrodes, thereby causing(a) concentration of said ionizable material in the zone containing saidprimary deposition electrode, and (b) concentration of said ionizingelectrolyte in the zone containing said primary electrode of saidopposite polarity.

In another aspect my invention is call apparatus for the subject liquorscomprising: a tank for a body of the liquor; primary opposed electrodesat the electrical extremities of said tank; at least one secondaryelectrode interposed between said primary electrodes, said secondaryelectrodes being pervious to the ions in said body of liquor andcompartmenting said body into a plurality of zones communicating witheach other through said secondary electrodes; and means for applyingelectrical poten-tial between said primary electrodes with the resultingpotential between adjacent electrode pairs being insufficient forcausing electrodeposition of said ionizable material on any of saidsecondary electrodes. 7

Further aspects of my invention involve combining the foregoing with theprinciples of my copending U.S. Pat. applications, Ser. No. 76,31 1,Ser. No. 94,267 and/or Ser. No. 91,905.

In the first such combination percolation of ionizing electrolyte isobtained through a porous primary electrode opposite the depositionprimary electrode and at least about 1/32 inch thickness. Such electrodeforms a boundary area of the tank. In the second such combination aporous primary deposition electrode forms a boundary area of the tank;such primary deposition electrode can be operated to obtain anelectrodeposit of said ionizable material; and pressure is provided forforcing resulting electrodeposited material through the pores of saiddeposition electrode; alternatively, no such electrodeposit is effected,but rather liquid medium enriched in said ionizable material is forcedthrough the porous deposition electrode.

The drawing shows in cross-sectional elevation a cell apparatus forconcentrating and recovering aqueous electrocoating paint dispersion.Item 2 is a horizontal, cylindrical casing of clear acrylic plastic. Thedispersion is passed upwardly and into the cell through inlet 3,suitably by pump not shown or an elevated reservoir of the dispersion.The dispersion can be circulated through the apparatus by withdrawing astream through outlet 4 and returning it to the pump suction reservoir.Alternatively, outlet 4 can be used simply as a vent for gases and canbe throttled with a valve if desired, whereby input liquid flows to theright and left.

In the cell porous secondary electrodes 16, 17, 18, and 19 are held inplace vertically by cylindrical spacers of the same plastic, the spacersbeing numbered, 5, 6, 7, 8, and 9. Each such secondary electrode issealed at its junction with the spacers by O-rings and hot meltadhesive, not shown, to prevent bypass of liquid around them. Theprimary electrodes are porous plates and 21, respectively. Primaryelectrode 15 is fitted into funnel 22 which is necked down to passthrough insulating plug 11 and flange 13. Flow through this electrodecan be throttled by valve 23 to pass through outlet 24. Primaryelectrode 21 is fitted into funnel 25 which necks down to pass throughplug 12 and flange 14. The flow through this electrode can be throttledby valve 26 to pass through outlet 27.

Vents 28, 31, 33, and 35 arise from their several chambers to vent offgas, and these can be throttled, if desired, by valves 29, 32, 34, and36, respectively. In place of the valves shown in the apparatus, thevents and liquor outlet can simply be extended upward to providewhatever the liquid head is desirable on the apparatus to prevent flowof liquid from the vents and to regulate back pressure on the primaryelectrodes relative to pressure of the inlet liquor. Flanges 13 and 14hold the apparatus intact with thrubolts in tension, the thrubolts notbeing shown in the drawing.

In operation one of the primary electrodes is charged anodically and theother cathodically from an external dc. power source not shown. This canbe done simply by making the protruding funnels ofelectricallyconductive metal and having the electrical connectionexternal to the flanges. Then, if the anolyte is an aqueous dispersionof anodic electrocoating paint binder (optionally with otherelectrodepositable paint components), typically one like that describedin Example 1 of U. S. Pat. No. 3,230,162, and primary electrode 15 ischarged as the anode, electrode 15 is the deposition electrode forconcentrating and recovering an anolyte comprising such paint binder. Insuch instance the electrode 21 is the cathode, and catholyte of aqueousbase solution passes therethrough.

If, however, the electrocoating paint dispersion to be treated has acathodic binder, such as the paint bath shown in Example 1 of U. S. Pat.No. 3,455,806 (copolymer resin with tertiary amine functionality ionizedwith acetic acid), cathode 21 would be the deposition electrode andanode 15 would be the electrode for passage of aqueous acidic solution.

In one mode of operation the voltage across the primary electrodes andthe positioning of the various electrodes is done so that no depositionoccurs on or in any electrode. However, if desired, the voltage acrossthe electrodes and positioning of the deposition electrode can be suchthat a concentrated emulsion or resinous deposit collects at the face ofthe deposition electrode and is drained therethrough for recovery. Itshould be recognized, however, that the primary electrodes 15 and 21 canbe made impervious, if desired, and a concentrated anolyte withdrawnfrom the cell through vent line 28 while a concentrated catholyte iswithdrawn through vent line 35.

Preferentially the secondary electrodes are porous metal plates at leastabout l/32 inch thick, as are the primary electrodes. However, theprimary deposition electrode can be made very coarsely foraminous ifdesired and covered, for example, with a non-conducting porous membranesuch as Dutch twill weave of nylon or polyester cloth having reasonableporosity, e.g., about l5-50 microns up to 150 microns, or even moreporous than this. Such membrane-covered electrode often is adequate forpassing emulsified concentrates of resinous and gel-forming materialsthrough it. However, if a film or body of resin or gel is to bedeposited on such electrode, an uncovered, fully electricallyconductivedeposition electrode is distinctly preferred to reduce pluggingtendencies.

In most instances the operation of the electrolytic cell apparatus willbe done with aqueous liquids at or above room temperature,advantageously above F., and preferably at about l20l 40F. whenseparating and collecting an electrocoating paint binder or paintconcentrate through a porous electrode. Lower temperature can be usedwhen desirable or necessary, provided that the liquor (and theelectrodeposit therefrom when it is being separated through anelectrode) are in fluent condition and can be made to flow underpressure. Other electrically-conductive media susceptible toautoionization such as glacial acetic acid, acetic anhydride, HCN,hydrazine, hydroxylamine, 80,, HF, H 50 COCl acetonitrile, anitromethane, liquid ammonia and tetrahydrofuran are contemplatedbroadly also in the liquid phase where their oxidative and otherdangerous properties can be controlled safely. Operating pressures andthe materials of construction would, of course, be designed accordingly.

In general temperature of liquor in the cell is restrictedadvantageously to avoid boiling of the liquor with attendant fumes, etc.and such temperatures also are restricted to diminish undesirableemissions or degradation of material in process if such considerationsare important in the operations. However, where a high temperature canbe tolerated, such as one approaching or reaching the boiling point ofthe liquor in process under the prevailing pressure conditions, one canuse such high temperature advantageously for further reducing viscosityand electrical resistivity of any film deposited on the depositionelectrode.

The pressure used must be at least slightly positive on the depositionside of the porous primary deposition electrode to forceelectrodeposited material therethrough. Usually a few inches of waterpressure differential across such electrode is adequate and is suppliedhydraulically, by pump, but much higher pressure can be used, e.g., 20or 30 psig. or even greater where the equipment can tolerate suchpressure. Optionally, however, other conventional pressure means can beused for such forcing, e.g., pressure rolls, pistons, Squeegees, and thelike. Pressure on the opposite electrode generally is exertedhydraulically by pump, and only a slight differential across theopposite electrode, if it is porous, is needed to force passage ofdissolved electrolyte very adequately. Naturally, higher pressure can beused for this purpose, and highest overall voltages give greatestelectrical construction against the passage of ions of the same chargeas such primary electrode through such electrode.

Absolute permeability of porous electrodes for use in this invention isdefined in and can be tested in accordance with the procedure shown inproposed SAE Aeronautical Information Report (AIR-887), Mr. lRobert i.Gross, 1965, Aircraft Porous Media, lnc., Glen Cove, New York,designated as APM-FSR-26.

The electrodes advantageously are made of metal, e.g., A.l.S.l. 300 and4-00 series stainless steels, monel, nickel, lnconel, or the like, andare best substantially inert to all the components of the liquor.Alternatively they can be built of electrically-conductive carbon suchas graphite or of metal-coated ceramic or plastic, or the like, or evenone or more very fine electricallyconductive screens or sieves, orpowdered metal pressed and sintered onto a screen. Such electrodes neednot be self-supporting, but can be enclosed in a coarsely foraminoussupport casing if desired. The preferred porous electrodes here areporous austenitic stainless steel plates because of their effectiveness,their resistance to attack, and their structural strength. Ordinarilymany of these are scaled alphabetically typically as follows by thePall-Trinity Micro Corporation, Cortland, New York, USA.

C D E F G H Mean Pore Size,

Microns 165 65 35 2O 1O 5 Absolute Porosity for Liquids,

Microns 160 55 35 25 l5 12 The selection of suitable porous electrodesfor the cell to some extent is determined by the kind of liquor beingproc-essed and desired degree of solids concentration, separation, andelectrolyte filtration which is wanted from the liquor. Thus, I havefound that the treatment of rinse waters from electrocoating baths likethat of Example 1 of U. S. Pat. No. 3,230,162 can use advantageouslysuch E or E" grade porous stainless steel cathode plate for dewateringand removing amino materials; C-D plates for permeable anodes in suchinstance appear to be excellent for obtaining permeation of resin orpaint concentrates. On the other hand, baths like that shown in Example3 of said patent appear to me to be better processed for removing aminomaterials with an electrode plate of about G porosity.

Because there is needed flow of ionic materials in both directionsthrough the secondary electrodes, it is best to make these of bed depthof at least one thirtysecond inch and preferably one-eighth inch toonefourth inch to provide an appropriate electrical field. Even thickerbeds can be used if they have virtually no electrical resistance, e.g.,one-half inch and up. The absolute porosity of liquid for such secondaryelectrodes broadly is effective between about one micron and a littleless (e.g., 800 millimicrons) up to about 200 microns, advantageouslyfrom 5-100 microns, and preferably from about 12-50 microns. The minimumporosity can be much smaller, but plugging is more apt to occur and theexpense is much greater to make and use. They must pass the dispersedparticles to achieve concentration. 0n the other hand, if the absoluteporosity is substantially greater than about 200 microns, the celloperation can be fairly delicate and difficult for achieving muchseparation or concentration of ionizing electrolytes at useful voltages.The absolute porosity of the primary electrode opposite the depositionelectrode for permeation of the ionizing electrolyte solution, if suchelectrode is to be porous at all, should follow the same criteria. Theabsolute porosity of the deposition electrode advantageously is betweenabout 50 and 200 microns and preferably between and 200 microns,although it can be finer with attendant finer filtration and slowerrate, or coarser if substantially effective sealing by theelectrodeposit occurs to prevent electrolyte ma terials of oppositecharge from too much penetration.

However, if desired, either porous primary electrode face towards theliquor in the cell and one or both sides of each secondary electrode canbe covered with a nonconducting porous filtering barrier such as afabric, suitably Dutch twill cloth, filter paper (although this is aptto deteriorate fairly soon in some liquors), a mat or weave or knit ofglass fiber, synthetic fiber, or the like. Such element can act torestrain liquid flow through the electrodes and can stop penetrationthereof by very coarse material in the liquor. For the secondaryelectrodes and the deposition electrode, it is advantageous that suchfiltering barrier have absolute porosity of about 800 millimicrons to200 microns and preferably between about 50-200 microns. For the porousprimary electrode opposite to the deposition electrode such barrieradvantageously has porosity of from 5-100 microns and preferably fromabout 12-50 microns. When such fabric, for example a twill with porosityof about 30-50 microns is used in this manner, all of the electrodes canbe made considerably more coarsely porous than stated above with stillquite useful transfer, collection, and separating ability. The coveringof the deposition electrode also assists in retaining heat about suchelectrode for increasing fluidity and lowering electrical resistivity ofdeposits such as resin. As ionic resins are now utilized in some casesfor assisting in filtration of sewage, it is conceivable that suchresins can be recovered in accordance with the invention principlesthrough porous electrode members.

The voltage between anode and cathode of the cell apparatus should benet unidirectional. it can be pulsed or have shaped nodes, butpreferably is rectified a.c. but with not more than about a 15 percentripple factor for best results. Where straightline dc. power isavailable, this power, of course, can be used with excellent effect.

The voltage used is generally above that necessary to electrolyticallydissociate some of the vehicle of the liquor. In most cases, the liquoris aqueous, and such dissociation is above about 1.8 volts, wherebyhydrogen is liberated from the cathode and oxygen from the anode.

The currently most used electrocoating paints include pigmented andclear-depositing materials. They comprise or consist of film-formingresinous binder dispersed in water with aid of ionizing agent(electrolyte) that ionizes at least a portion of ionizable sites in theresin which forms a significant fraction of said binder. Ordinarily suchdispersion will contain additionally or ganic solvents, plasticizer,anti-foam agents, wetting agents, and if pigmented, will containpigments, fillers, optional stains and colorants, heat fusible orpractically infusible resin particles, metal particles, glass fritoccasionally, synthetic and natural latices, etc. Concentrates of suchpaint usually contain 0-70 percent water and often have no, or verylittle, ionizing agent in them.

My studies have indicated, as pointed out in U. S. Pat. application,Ser. No. 76,31 1, that the invention can be used to achieve a degree ofseparation of various kinds of pigments from dispersion, therebyconcentrating carbon black with respect to titania, titania with respect to clays, etc. if desired.

To preclude electrodepostion of said ionizable material, e.g., anelectrocoating paint binder on a deposition electrode or any secondaryelectrode, the voltage difference between such electrode and its opposedadjacent electrode in the pair should be below that which would causesuch deposition in or on the electrodes.

For a particular liquor and electrodes at a given spacing, e.g., 2.5cm., the maximum voltage before incipient deposition can be tested in asimple cell without agitation by raising the voltage between the twoelectrodes from zero and noting when the rise in current flow by ammeterbetween them breaks with increasing voltage and begins to level off ordrop, indicating incipient deposition. For conventional anodic paintdispersion such as that shown in Example 1 of U. S. Pat. No. 3,230,162at about percent concentration of resinous binder in the dispersion at80F. and quiescent cell conditions, the maximum voltage which can beused is about 5 volts, such maximum voltage would be about 8-9 volts forabout 1 percent concentration of the same resinous binder. The effect oftemperature is broadly inverse to liquor electrical resistivity.

In this application and in its parent applications, when a voltage orelectrical potential between adjacent electrode pairs insufficient forcausing electrodeposition of the ionizable material on electrodes, e.g.,secondary electrodes, is referred to, it will be understood that what ismeant most accurately is that such electrodepositing material isredissolved at a rate equal to or faster than it is being deposited onsuch electrode. Accordingly, the net deposition is nil.

Minimum deposition voltage thus can be considered to be the highestelectrical potential (voltage) above the decomposition potential of theliquid medium, most commonly water, that will support a Faradic current(ampere) flow capable of electrodepositing such material at a rateexactly equal to the redissolving rate of such deposit. Factorsaffecting such deposition include fluid flow over the electrode surface,concentration of ionizing electrolyte for such depositable material, pH,temperature, and electrical conductivity of the liquor present in thevarious chambers.

At a constant applied voltage, a decrease in ampere flow indicates anincrease in system electrical resistance due to a deposition rate inexcess of the redissolving rate of the electrodepositable material onthe electrode. An increase in ampere flow indicates a decreasing systemelectrical resistance and such deposition rate less than theredissolving rate on the electrode. A constant ampere flow thenindicates a deposition rate equal to the redissolving rate of thedepositable material onto an electrode.

The equipment preferably is arranged so that gas generation does notcause changes in the resistance of the system because of diminution inelectrode surface area available for contact with the bath.

In some respects, the apparatus with multiple secondary electrodes hassome of the aspects of a plate and frame filter press. The apparatusneed not be fed symmetrically as shown in the drawing, but fedasymmetrically. Thus, for example, anodic resin appears to separate andconcentrates with greater facility than does its ionizing amine. Hence,it can be valuable in some cases to devote more chambers to theconcentration of the amine. In some cases it may be desired also toconcentrate certain pigments relative to others by secondary electrodespacing and/or making the secondary electrodes more or less porous withrespect to one another so that clay will tend to enrich in one chamberon the resin concentration side of the cell, titanium at a farther one,and carbon being the richest in the most remote one adjacent to thedeposition electrode.

The following examples further delineate my invention, but should not beconstrued as limiting it. In this application, all parts are parts byweight, all percentages are by weight, and all degrees are in degreesFahrenheit, unless otherwise expressly indicated. Nonvolatile matter(NVM) is reckoned as the residue on curing a sample of the subjectliquor at 350F. for 50 minutes.

EXAMPLE 1 An open-top, rectangular, non-conducting plasticelectrocoating tank had a primary electrode at each end and was dividedinto three zones of equal size with two vertical secondary electrodes.Each electrode was an impervious, phosphate-treated, cold-rolled steelsheet sealed to the long tank sides and to the bottom. Each zone in thetank, labeled A, B, and C from left to right, was filled to the samedepth with a conventional aqueous anodic electrocoating paintdispersion. The end electrode on the right-hand side was the primarycathode. The end electrode on the left-hand side was the primary anode.

Preparation of the resinous binder concentrate and the pigment has beendescribed in Example 1 of U. S. Ser. No. 76,311 (that is, resin based onvinyl toluenated, maleinized linseed oil, extended with non-heatreactive phenolic resin and ionized with morpholine).

Pigment, resinous binder concentrate, and sufficient water was blendedtogether to give a stable dispersion of 12 percent by weight NVM with a3:1 weight ratio of binder to pigment. At a temperature of 77F, theprimary (end) electrodes were charged with 100 volts across them from anexternal source for two minutes (rectified a.c. with about 5 percentripple factor). The primary cathode received no coating; the primaryanode coated on its right side; the two secondary electrodes coated ontheir right sides only. No coating appeared on the left side of any ofthe electrodes, including the left side of the anode which was not incontact with the paint dispersion.

The left-hand secondary electrode functioned as a cathode with respectto zone A, and the right-hand secondary electrode a cathode with respectto zone B. These plate electrodes were spaced 10 cm. apart. Each side ofthe electrodes exposed to the bath had square centimeters of area.Specific resistivity of the bath at 77F. was 625 ohm/cm.

The coating was as follows:

Primary anode 0.098 grams or about 0.29 mil thickness;

Left Secondary Electrode 0.23 mil thickness;

Right Secondary Electrode 0.22 mil thickness. Calculated total bathresistance across the cell from primary anode to primary cathode(without any coating) was 222 ohms. First recording of current flowindicated total resistance of 271 ohms between primary electrodes.Current flow at the end of the two minutes indicated coating plus totalresistance of 3,522 ohms. The total deposited film resistance was about3,300 ohms.

0.083 grams or about 0.080 grams or about Calculated voltage drops,using current flow and grams of coating applied to determined zoneresistances, provided the following voltage distribution: Primarycathode to right secondary electrode 31 volts; right secondary electrodeto left secondary electrode 32 volts; and left secondary electrode toprimary anode 37 volts.

Based on this data, if porous secondary electrode plates are substitutedfor the impervious secondary electrodes and 12-15 volts are appliedacross the cell from primary anode to primary cathode, zone A willbecome enriched in electrocoating paint solids and zone C in ionizingamine without deposition of any paint solids on any of the electrodes.

EXAMPLE 2 The apparatus used was like that of the drawing, except thatno valves were placed on outlet and vent lines. lnstead, vents 28, 311,33, 33, and outlet 4 were merely run vertically upward to act as gasvents and to maintain a static head on the apparatus. Anode 115 on theleft drained through outlet 24, without a valve 23, and upward to aheight regulated to put back pressure on the anode. Similarly, cathode21 on the right drained without a valve 26 through outlet 27 raisedupward to regulate height to put back pressure on the cathode. The fluidheads were measured from the horizontal center axis of the cylindricalapparatus in terms of inches of liquor in the vertical legs. Rectifiedac. power like in Example 1 was used.

Each electrode face had a 2% inch diameter area exposed to the liquorand was one-eighth inch thick, porous A.l.S.l. 316 stainless steelfurnished by the Fall- Trinity Micro Corporation. The electrode pairswere spaced one from another, 5 cm. on center. Temperature was 77801F.

The electrode porosities were as follows: Anode 115 was a G gradePall-Trinity Micro Corporation plate; cathode Zll had about one micronabsolute porosity; secondary electrode 116 was an 1E" grade plate of thesame company; secondary electrodes l7 and lid were D grade plates of thesame company; and secondary electrode 19 was an F grade plate of thesame company.

An aqueous anodic electrocoating paint dispersion made from a resinousbinder concentrate like that of Example 1 of U. S. Ser. No. 76,311 wasionized and dispersed in deionized water with morpholine to give adispersion concentration of 5.37% NVll/l.

One run at 20 volts d.c. between anode l3 and cathode Zl was made byfeeding the aqueous ionized resin dispersion through inlet 3 at a fluidhead of 37 cm. Back pressure against both anode 115 and cathode 211 was20 cm. The anolyte concentrated to 6.09% NVM flowing at 6 grams perminute while the catholyte under these conditions was reduced to 4.72%NVM, flowing at 2 grams per minute.

After a small amount of running the cathode flow slowed somewhat. At thesame 20 volts between anode and cathode the back pressure on the anodewas lowered to 16 cm. and the back pressure on the cathode to zerogauge. The NVlVl of the anolyte was 6.02% flowing at 2.8 grams perminute while the cathode flow was at one gram per minute and 4.11%NVlVl. During a running the right-hand cell chamber nearest the cathodecleared up considerably.

The voltage was raised to 30 volts between anode and cathode and thefeed head to 64 cm. Back pressure on the anode was 20 cm. and zero gaugeon the cathode. Voltage drops between the live vertical metal tubes (4,20, 311, 33, and 35) were measured and found to be about 5 volts betweeneach pair of adjacent tubes. The anolyte flow was two grams per minuteat 7.17% NVM, a concentration of 34 percent based on the feed. Thislater declined to slightly over 1.5 grams per minute at 8.06 percentNVM, a concentration of 50 percent based on feed.

The catholyte flow was 0.3 grams per minute at 1.26% NVM, a decrease of76 percent in NVM. Later this increased to 0.5 grams per minute at 0.53%NVM, a percent decrease in NVM. in no instance on any of the tests didnoticeable electrodeposition of resin occur on or in any electrode.

While the foregoing examples have described treatment of aqueouselectrocoating paint compositions containing an amine as ionizingelectrolyte for the resin, it should be understood that other bases,e.g., those containing potassium, sodium, lithium, aqua ammonia, andmixtures of such bases with each other and with amines, are suitable forsimilar processing.

What is claimed is: l. in a process for the electrolytic treatment of anelectrically-conductive liquor which contains dispersed ionizablematerial electrodepositable therefrom onto a deposition elec-trode tobuild electrical resistance thereon and dissolved ionizing electrolytefor said material, the improvement for separating anolyteenriched andcatholyte-enriched liquids from said 1iquor which comprises:

forming a body of said liquor with primary opposed electrodes at itselectrical extremities, said primary electrodes being a depositionelectrode and an electrode of opposite polarity and obtaining theircharge from a source external to said body;

interposing between said primary electrodes at least one secondaryelectrode deriving its charge from the electrical conductivity of saidbody, the secondary electrodes being pervious to the ions in said bodyand compartmenting said body into a plurality of zones communicatingwith each other through said secondary electrodes;

applying an electrical potential between said primary electrodes withthe potential between adjacent electrode pairs being insufficient forcausing electrodeposition of said material on any of said secondaryelectrodes, thereby causing concentration a. said ionizable material inthe zone containing said primary deposition electrode, and

b. concentration of said ionizing electrolyte in the zone containingsaid primary electrode of opposite polarity.

2. The process of claim ll wherein said primary electrode of oppositepolarity to said deposition electrode is pervious to dissolved ionizingelectrolyte and is disposed to form a boundary area of said bath.

3. The process of claim ll wherein said primary deposition electrode isdisposed'to form a pervious boundary area of said body, and saidionizable material is forced through the pores of said depositionelectrode.

4. The process of claim 3 wherein said liquor is aqueous and saidionizable material comprises an electrocoating paint binder.

12 is an anodic paint binder, and said primary deposition electrode isan anode.

7. The process of claim 4 wherein said paint binder is a cathodic paintbinder, and said primary deposition electrode is a cathode.

2. The process of claim 1 wherein said primary electrode of oppositepolarity to said deposition electrode is pervious to dissolved ionizingelectrolyte and is disposed to form a boundary area of said bath.
 3. Theprocess of claim 1 wherein said primary deposition electrode is disposedto form a pervious boundary area of said body, and said ionizablematerial is forced through the pores of said deposition electrode. 4.The process of claim 3 wherein said liquor is aqueous and said ionizablematerial comprises an electrocoating paint binder.
 5. The process ofclaim 4 wherein the temperature of said primary deposition electrode ismaintained substantially above room temperature for reducing viscosityand electrical resistivity of electrodeposited material.
 6. The processof claim 4 wherein said paint binder is an anodic paint binder, and saidprimary deposition electrode is an anode.
 7. The process of claim 4wherein said paint binder is a cathodic paint binder, and said primarydeposition electrode is a cathode.